Evacuees, who are afraid of possible a nuclear power plant meltdown in Fukushima Prefecture, and vacationers queue up to check in their flights at Narita International airport on Thursday, March 17, in Narita, Japan.

The exodus – along with concerns about levels of radiation reaching Tokyo – has caused many airlines to rethink their Tokyo routes and schedules. And the entire airline industry seems to be anxiously eyeing the demand for flights to the regional hub.

Air France, Swiss Air, and British Airways are among the airlines continuing their service to Tokyo, but they are including stopovers in other Asian cities so that their flight crew can switch over there instead of spending a night in Tokyo, according to their websites.

"A walk-up fare below $1,000 is quite low and likely related to a drop in demand," said Dan Toporek, a spokesman for online travel agent Travelocity.com. "It’s too early to tell what the long-term impact will be."

The Bloomberg US Airlines Index slumped 6.4 percent from March 11 through yesterday, outstripping the 3.6 percent drop for the Standard & Poor’s 500 Index. Delta’s 9.2 percent slide was the most among 12 carriers in the Bloomberg gauge, followed by the 7.7 percent tumble for United Continental.

Continental Airlines was the first US airline to disclose that demand for flights to Japan was on the decline, according to Bloomberg. It hasn't made any changes to its schedule yet, but may cut some flights to Japan based on demand.

American Airlines is also keeping its normal flight schedule to and from Japan, so far.